The violation of the charge neutrality conditions

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The violation of the charge neutrality conditions

Postby MasoudMS » Sat Aug 03, 2019 9:31 pm

Dear users, Hi
I performed a phonon calculation on a full relaxed structure at the Gamma point.
After doing ANADDB, in the output file, the violation of charge neutrality for one displacement and direction is obtained about 0.19 and for most of the directions, the violations are zero or of order 0.002. Is this violation a critical error or I can ignore it?
My input and output files are attached.

Thanks
Masoud
Attachments
ifc.in
input file
(316 Bytes) Downloaded 6 times
ifc.out
output file
(232.56 KiB) Downloaded 8 times
MasoudMS
 
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Re: The violation of the charge neutrality conditions

Postby ebousquet » Mon Aug 05, 2019 10:17 am

Dear Masoud,
The charge neutrality is indeed violated by about 0.2e but your Born charges are around 3e, meaning that the violation is about 6%, which is fair.
It depends how much precision you want for the Born charges for example, or related properties, for example if you want to analyse variation of Born charges that are less or around 0.2e then you should improve the precision.
If you want to improve it, you can increase the number of k-point in the direction it is deviating the most.
Best wishes,
Eric
ebousquet
 
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Re: The violation of the charge neutrality conditions

Postby MasoudMS » Fri Aug 09, 2019 9:44 pm

Dear Eric,
Thanks for your answer.
According to your suggestion, I increased the k-point (ngkpt from 6 8 6 to 6 14 6) and the violation of charge was decreased (from 0.2e to 0.07e).
Although this change has a small effect on the phonon frequency, the electronic contribution of the dielectric function has a considerable change.
Also, three acoustic phonons have now a small negative value. My previous acoustic phonons were exactly zero. Is this trend normal or I must try with more k-point?

Thanks,
Masoud
MasoudMS
 
Posts: 3
Joined: Sun Jun 02, 2019 3:51 pm


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